The present invention relates to a method for surface-processing of a base of a photoreceptor for electrophotography, and more specifically to a method for surface-processing of a base, which is made from an aluminum material, of a photoreceptor for electrophotography.
In an electrophotographic copier, a digital copier, a laser printer, or the like, an electrophotographic photoreceptor on which a photoconductive layer is provided on a base of a rotatable drum-like electrophotographic photoreceptor (which is called "base", hereinafter), is commonly used. As a material of the base, an aluminum material is preferably used since it is low in cost, light in weight, processing is easy, and the like. The rotatable drum-like base, which is made from aluminum material, is generally made by machining the surface of a pipe, and a cutting liquid is normally used at that time. This cutting liquid is used for the purpose of cooling, lubricating and cleaning, and specifically, petroleum, polybutene, kerosine, white kerosine, or the like are used for the cutting liquid. Further, in order to prevent an image defect, cleaning is conducted also on the surface of the base by a contact type cleaning means utilizing a brush or an abrasive material after machining of the base.
The following technologies have been proposed conventionally as specific technologies relating to a method for surface-processing of a base of a photoreceptor for electrophotography:
(1) Technology in which machining of an electorophotographic photoreceptor base is conducted by using a cutting oil which contains not more than 1.0 weight % of an oiliness improver and/or an extreme pressure additive. (Japanese Patent Publication Open to Public Inspection, (hereinafter, called Japanese Patent O.P.I ) No. 307463/1988.)
(2) Technology in which a surface of an electrophotographic photoreceptor base made from aluminum alloy which contains silicon, copper, and titanium in a ratio of a specific range is machined by means of a cutting tool having roundness on a cutting portion. (Japanese Patent O.P.I. No. 86151/1989.)
(3) Technology in which an electrophotographic photoreceptor base made from aluminium alloy which contains silicon and iron in a ratio of a specific range, is used. (Japanese Patent O.P.I. No. 86152/1989.)
(4) Technology in which a surface of an electrophotographic photoreceptor base made from aluminium alloy which contains silicon, magnesium, and iron in a ratio of a specific range, is machined by means of a cutting tool having roundness on a cutting portion. (Japanese Patent O.P.I. No. 86153/1989.)
(5) Technology in which an electrophotographic photoreceptor base made from aluminium alloy which contains silicon, magnesium, and iron in a ratio of a specific range, is used. (Japanese Patent O.P.I. No. 86154/1989.)
(6) Technology in which an electrophotographic photoreceptor base made from aluminium alloy which contains magnesium, silicon, copper, and titanium in a ratio of a specific range, is used. (Japanese Patent O.P.I. 86155/1989.)
(7) Technology in which an electrophotographic photoreceptor base made from aluminium alloy which contains silicon, iron, and magnesium in a ratio of a specific range and other metal in not more than a specific ratio, is used. (Japanese Patent O.P.I. 123245/1990.)
(8) Technology in which a surface machining apparatus which is composed of a lathe unit, a high pressure liquid blasting unit and a conveyance unit for an electrophotographic photoreceptor base, and by which lathe machining and pressure liquid blasting can be automatically conducted in succession, is used. (Japanese Patent O.P.I. No. 172573/1990.)
(9) Technology in which a specific nozzle apparatus for cutting liquid supply having a main shaft head which rotatably supports a main shaft to which a rotating tool having an oil hole and a rotating tool not having an oil hole are provided, is used. (Japanese Patent O.P.I. No. 152642/1987.)
(10) Technology in which high pressure water is blasted from a jet nozzle which is connected with a high pressure water supply source onto the surface of an electrophotographic photoreceptor base so that it may be scanned by the nozzle and roughened into a predetermined surface roughness. (Japanese Patent O.P.I. No. 264764/1988.)
However, in the conventional technology, there is a possibility that environmental foreign material such as cutting powder of aluminium, dust and refuse, and stain or the like deposits firmly on a surface of a base made from aluminium material which is surface-machined using a cutting oil, as they are contained in the cutting oil. When left for a period more than a month, for example, especially under high temperature and high humidity in summer, the aforementioned deposit becomes more firmly attached, and corrosion is caused partially on the surface of the base. There is a case in which the corrosion can not be recognized by visual observation.
The aforementioned type of corrosion can not be perfectly eliminated by the method in which the base is dipped into an organic solvent or an interfacial active agent solution, or is cleaned by means of noncontact cleaning such as ultrasonic cleaning or ultraviolet/O.sub.3 irradiation cleaning. Accordingly, when a photoreceptor layer is provided on a surface of a base, on which corrosion exists, an image defect is generated on the corroded portion and especially, when the photoreceptor layer is applied to an image forming process in which a non-contact developing method is adopted, there are problems in which black spots, black stripes, and a partial gray background are generated.
Partial corrosion on the surface of the base can be almost completely eliminated by the method in which the aforementioned surface of the base is cleaned by contact-cleaning using a brush or abrasives. However, the surface of the base is damaged depending on the kind of aluminium material, and since the film thickness of a photoconductor formed on the flaw, especially that of a carrier generation layer, tends to be changed, and photo-sensitivity of the photoreceptor layer is changed, there is a problem in which contrast is generated in a half tone image, which results in an image defect.
Furthermore, in the base made from aluminium material having a surface roughness of 0.3 to 2.0 .mu.mR.sub.max and some 5 to 15 minute grooves within 0.1 mm in length, oil, cutting powder, or environmental foreign matter become deposited in the minute grooves, and when left, since the stuck matter can not be removed only by a brush or abrasives, it causes an image defect. Therefore, sometimes, an electrophotographic photoreceptor base of high quality can not be obtained.
Furthermore, in the base made from aluminium material the surface of which is machined by using cutting oil as in the case of the prior art, it is necessary to clean by using a chlorine solvent such as trichloroethylene, 1,1,1-trichloroethane, perchloroethylene, methylene chloride, and the like in order to remove cutting oil sufficiently. Accordingly, using a large quantity of such a solvent causes problems of environmental contamination and working safety from the viewpoint of ozone layer destruction, carcinogenicity, and the like.
Furthermore, in the aforementioned engineering (10), since processing of a surface of the base is conducted by jetting high pressure water, uniform processing is difficult.
Inventors of the present invention have found causes of the generation of image defects as follows: cutting powder and environmental foreign matter generated at the time of surface processing of the base become deposited on the surface of the base making the cutting oil act as a binder; or the cutting oil itself is decomposed to deposit firmly on the surface of the base; or the cutting oil is deposited firmly on the surface of the base through chemical reaction. Furthermore, the inventors have found that when the cutting liquid is water or an aqueous solution composed of an interfacial active agent or a soluble organic solvent, instead of the cutting oil, and the surface of the base is machined by a cutting tool made of a sintered polycrystal diamond, image defects are reduced, cleaning after processing is easy, and freon or a chlorine solvent are unnecessary, or even when they are used, only a small quantity is used. The inventors of the present invention have found that it is possible to provide an electrophotographic photoreceptor base of high quality, and have completed the present invention.